This invention relates in general to a lockset and more particularly to a lockset assembly in which the latch bolt is extendable into a dead bolt function.
With the usual latch bolt type lockset, the bolt extends about one-half inch from the front of the lock. Taking into consideration the gap that exists between the door jamb and the door, even less of the length of the latch bolt is available for engagement with the door jamb. Accordingly, with this type of lock, one possible way of obtaining unlawful entry is to spread the door jamb further away from the door to have the latch bolt clear the strike and the lock will no longer serve to maintain the door closed.
In view of the above, it has become increasingly popular to add an auxiliary dead bolt lock to the door. However, the use of such an auxiliary dead bolt does present some problems. For example, its use requires a second hole to be drilled in the door as well as requiring the mounting of an additional mechanism. Also it may require the use of a separate key if the latch bolt cylinder and the auxiliary dead bolt cylinder are not keyed alike. In addition, the latch bolt mechanisms as well as the auxiliary dead bolt are normally capable of being locked on the inside. In an emergency situation, it would take two actions by the person in the inside to retract the latch bolt and auxiliary dead bolt to open the door and have egress therefrom.